The invention relates to sensing devices, and more particularly to multivariable sensing devices.
Radio frequency identification (RFID) tags are widely employed for automatic identification of objects (e.g. animals, garments, etc.) and monitoring and detection of containers (such as, unauthorized access to contents of containers). Generally, RFID readers are used to obtain digital data from the RFID tags for such automatic identification. Digital data may include, for example, digital identification of the tag, or any other information written and/or stored in a memory chip of the RFID tags. The RFID tags transmit electromagnetic signals at different relative levels of transmitted power at different times. Signals received by the RFID reader in combination with the transmitted relative power levels of the received signals from the RFID tags are employed to locate the RFID tags, and read the digital identification information from the RFID tags (e.g., from a memory chip or a back-reflector structure of a RFID tag).
Further, radio frequency based sensors are used for sensing physical, chemical and biological constituents in a sample. Moreover, the radio frequency based sensors are cost-effective, and easy to incorporate in a component or a system for measuring physical, chemical or biological constituents of the component or the system. Typically, analog or sensor data from the radio frequency based sensors is read using an impedance reader. Further, the sensor data is read with the help of a pick-up coil that is integral part of the radio frequency based sensor.